Method of determining a roadway curve radius

Abstract

A curve radius of a roadway is determined by measuring the difference in wheel speed of at least two vehicle wheels and the rate of yaw of the vehicle, and hence the curve radius, is determined therefrom. The wheel speeds are determined by measuring the time required for the wheel to rotate by a fixed rotational angle, based on a fixed number of pulses produced by a pulse transmitter which is part of an ABS or ASR system for the vehicle. The method provides considerably improved accuracy using simple, vehicle-contained components and various parameters can be taken into account simultaneously.

I claim:  
     
       1. A method of determining a roadway curve radius from the difference between wheel speeds of at least two unpowered wheels comprising assigning a constant rotational wheel angle to each wheel, measuring an aggregate time period for the wheel to rotate the assigned rotational wheel angle for each wheel, determining a ratio of the aggregate time periods for the wheels of a pair of wheels on one axle to rotate the assigned rotational wheel angle, and determining a transverse slip and hence the roadway curve radius from the ratio of the aggregate time periods. 
     
     
       2. A method according to  claim 1  wherein the constant rotational wheel angle is determined by preassigning a constant number of rotational pulses from a rotational pulse transmitter for each wheel. 
     
     
       3. A method according to  claim 1  including determining an “offset” equation of the time permits measured on all wheels by forming a mean of the ratios of the measured time periods. 
     
     
       4. A method according to  claim 3  wherein the offset equation is determined at preassigned time intervals. 
     
     
       5. A method according to  claim 1  wherein the beginning of time measurements on the wheels of a pair of wheels is synchronized.